Any updates on this? I tried a very similar approach to the one outlined in the blogpost that you provided and the performance degradation becomes tremendous when you have a scenario like year/make/model/partType of thousands of auto parts.

And since there is no top level category that we can use (like in the bikes--> mountain bike) scenario of the blog we really don't have good ways to address this (except for using a separate solution for facets like a Redis data store)